A tailgate which is a back door of a four-wheel vehicle is formed by connecting an outer panel on an outer side of the vehicle and an inner panel on an inner side of the vehicle to each other and by assembling door parts such as a door lock and a key cylinder between these outer and inner panels.
In a tailgate in Japanese Patent Laid-open No. Hei 8-142676, an inner panel is formed in a shape having an upper opening portion corresponding to a window cavity formed in an outer panel and a lower opening portion separated by a partitioning portion extending in a right and left direction relative to this upper opening portion, and a module plate in a substantially square shape which has a size large enough to cover this lower opening portion and to which door parts are attached in advance is fitted in the lower opening portion.
At present, a decrease in vehicle weight is being demanded in order to improve the fuel efficiency of a vehicle. Since a tailgate is a part of a vehicle, this tailgate influences the vehicle weight, but in the tailgate in the aforesaid conventional art, a sufficient measure is not taken for a weight decrease.
An object of the present invention is to provide a vehicle door which can realize a decrease in door weight and contribute to a decrease in vehicle weight and to provide a method of manufacturing the vehicle door.